In the perfectly controlled atmosphere of a brick-proof, hermetically sealed greenhouse deep in the Kent countryside, a fresh crop of tobacco plants is beginning to flourish.
There is nothing unusual about the plants' appearance, but they are none the less extraordinary. A genetic tweak ensures that every cell of every plant churns out tiny quantities of an experimental drug. When harvested, they could bring cheap medicine to millions.
Scientists say that the $15m project could provide a powerful weapon against Africa's HIV pandemic.
The process is called pharming, and to many it is both the future of GM crops, and the future of the drugs industry. If the tobacco plants in Kent are a success, each one will provide 20 doses of an anti-HIV drug - enough to protect a woman from infection for up to three months.
Pharming is a marriage of high and low technology that capitalises on the advantages of both. Instead of needing a $500m drug manufacturing facility that takes five years to pass regulatory approval, pharming uses simple crop-growing practices that have been honed over centuries.
Like other GM technologies, pharming is not without its risks. Pressure groups such as Friends of the Earth fear that if food crops such as maize or tomatoes are adapted to grow drugs in some regions, there is a risk of their contaminating maize or tomato crops.
Professor Julian Ma, who leads the tobacco plant project at the Centre for Infection at St George's hospital in south London, acknowledges that the plants, and more importantly their pollen, have to be contained. It is why the plants are being grown in $64,000 high-security Unigro greenhouses, which normally house experiments on plant viruses. Designed to withstand a lobbed brick, the greenhouses are twin-skinned plastic. Rupture either skin and the entire greenhouse is immediately flooded with formaldehyde, keeping everything inside.
At his labs at St George's, Prof Ma and his PhD student Amy Sexton have been producing the genetically modified tobacco plants and perfecting techniques to boost the amount of drug each plant makes. They take a common tobacco plant, Nicotiana tabacum, and punch small holes from the leaves. The circles of leaf are placed in a petri dish and then squirted with a liquid containing a genetically modified bacterium. When the bacterium infects a plant leaf, it inserts some of its own genes into the plant's DNA, in effect hijacking its cellular machinery, and tricking the plant to produce new proteins.
In the wild these proteins cause tumours that kill the plant. But in the laboratory the bacterium is made safe and doctored with different genes that fool the plant into making cyanovirin-N.
The researchers believe that cyanovirin-N could become a powerful weapon in the fight against HIV, as it prevents the virus from infecting human cells. They are keen to make a microbicide cream for women in Africa and other developing countries where many have little or no control over their partner's use of a condom. The evidence so far is that a microbicide cream could dramatically cut down the spread of HIV through sexual activity.
To produce enough cyanovirin to make any significant impact on the HIV pandemic will take a lot of plants. The team calculates that 5,000kg of cyanovirin would be needed for 10 million women to have two doses a week.
If the plants continue to grow well in Kent - at the home of the East Malling Research facility - Prof Ma hopes to have enough drug to conduct human clinical trials of the microbicide within three years.
